The present invention relates generally to the application of pressure to a workpiece and, more particularly, relates to the application of pressure to a workpiece solely by thermal expansion of the fixture holding the workpiece.
Increasing demands are emerging for higher performance semiconductor packages. To meet these demands, interconnection designs have been proposed using thin film technology, including multilayer thin film (MLTF) structures.
MLTF structures are composed of metal and dielectric layers comprising, among other materials, copper and polyimide. Such structures are used in the microelectronics industry to interconnect semiconductor devices (also referred to as chips). The interconnect structure includes alternating layers of electrically insulating and conducting materials. Vias in the insulating material provide electrical connections between the conductor layers and bond pad terminations on semiconductor devices. The number of conductor layers depends on the signal routing, grounding and shielding requirements for the interconnect structure.
Thin film structures can be fabricated in a variety of ways. In one method, the thin film structure is fabricated on a temporary substrate such as one made from silicon, ceramic, glass or polished metals. Once the thin film structure is complete, it is removed from the temporary substrate and then typically joined or laminated to a permanent substrate by the application of heat and pressure in a lamination press. The formation of such thin film structures and their joining to a permanent substrate is disclosed in Kelly et al. U.S. Pat. No. 6,036,809, the disclosure of which is incorporated by reference herein. The permanent substrate may also be selected from the same group of materials that are used for the temporary substrate.
Heretofore, the lamination of the thin film structure to the permanent substrate has been accomplished by hydraulic or pneumatic means. Hydraulic or pneumatic means for applying pressure in related applications, such as printed circuit board laminating, have been proposed by others such as Namysl U.S. Pat. No. 4,806,195, the disclosure of which is incorporated by reference herein. Numerous other references disclose printed circuit board laminating by the application of heat and pressure without disclosing the precise apparatus. Examples of the latter include DiStefano et al. U.S. Pat. No. 5,640,761, DiStefano et al. U.S. Pat. No. 5,570,504, Hamilton et al. U.S. Pat. No. 5,688,350, and Misfeldt U.S. Pat. No. 3,972,755, the disclosures of which are incorporated by reference herein.
Japanese Published Patent Application 55-031819, the disclosure of which is incorporated by reference herein, discloses a laminating apparatus including Teflon® “resin plates” in which the laminating pressure is applied by a pressing plate and a screw or bolt.
The typical apparatus for the application of heat and pressure to a workpiece, whether it is lamination as described above or some other application, has several deficiencies. The first is the typical apparatus is run in batch operation which restricts throughput. Another deficiency is that the typical apparatus requires large capital expenditures. A further deficiency is large capital expenditures to maintain sufficient tools to meet capacity needs. A last deficiency is the high operating costs associated with the operating and maintenance of the typical apparatus.
In view of the foregoing, it is a purpose of the present invention to have an apparatus and method for the application of heat and pressure that can be run in batch mode or continuous mode to optimize the throughput of the apparatus.
It is another purpose of the present invention to have an apparatus and method for the application of heat and pressure that substantially reduces capital expenditures for the tool itself as well as the number of tools to meet capacity requirements.
It is yet another purpose of the present invention to have an apparatus and method for the application of heat and pressure that has reduced operating costs.
These and other purposes of the present invention will become more apparent after referring to the following description of the invention considered in conjunction with the accompanying drawings.